2 5094 Pure Syllabus (a) state the roles of water in living organisms.(b) list the chemical elements which make up:• carbohydrates• fats• proteins(c) describe and carry out tests for:• starch (iodine in potassium iodide solution)• reducing sugars (Benedict’s solution)• protein (biuret test)• fats (ethanol emulsion)(d) state that large molecules are synthesised from smaller basic units:• glycogen from glucose• polypeptides and proteins from amino acids• lipids such as fats from glycerol and fatty acidsForm pptTurns colour

4 Constituents of Food So what can we find in food?Dietary Fibre (vegetables like cellulose are not digested)WaterNutrientsCarbohydratesProteinsFats (lipids)VitaminsMineral Salts

5 Roles of Water 70% of the Body is made up of WATER Lost of water byBreathingUrinationExcretion of faecesPerspirationExtreme loss of water may affect the homeostasis of the body causing many vital processes unable to function and may lead to death.

6 Roles of Water Water is used as a solvent Regulating body temperatureDissolves a range of substances that are useful or waste products.Eg: glucose, amino acids, mineral salts, urea.Regulating body temperatureWater enables the loss of heat from the body in the form of perspiration (Heat Capacity of water = 4.2 kJ/Kg°C)Prevent overheating of the body (fever)Supporting structureShape of eye maintained by aqueous and vitreous humour which is largely made up of water.Amniotic fluid in the placenta protects the foetus from mechanical stress.

7 Water plays a role as lubricantMucus in digestive and respiratory tractSynovial fluid in jointsCarries sperms in seminal fluidWater as a site of many reactionsWater is needed for transport of substances (diffusion & osmosis)Movement of water and mineral salts in the xylemDiffusion of carbon dioxide in the mesophyll layers in the leafWater as a reactant in photosynthesisWater used for dispersal of fruits (coconut)

15 Different Forms of PolysaccharidesStarch (Cell Sap) & GlycogenMany units of glucoseUsed as energy reserves in plants(starch) and animals(glycogen).Starch – long chains with few side branchesGlycogen – many side branchesCellulose (Cell Wall)Multiple units of glucoseArranged differently thus more difficult to breakUsed as a structural support in leaves and plantsReferred to as fibre

17 Function of CarbohydratesSimplest unit of Carbohydrate (Monosaccharides) provides energy for the human bodyIt releases energy during aerobic respiration in the cell’s mitochondria.Glucose is the most common form of monosaccharide.

24 5094 Pure Syllabus (a) state the roles of water in living organisms.(b) list the chemical elements which make up:• carbohydrates• fats• proteins(c) describe and carry out tests for:• starch (iodine in potassium iodide solution)• reducing sugars (Benedict’s solution)• protein (biuret test)• fats (ethanol emulsion)(d) state that large molecules are synthesised from smaller basic units:• glycogen from glucose• polypeptides and proteins from amino acids• lipids such as fats from glycerol and fatty acids

31 5094 Pure Syllabus (a) state the roles of water in living organisms.(b) list the chemical elements which make up:• carbohydrates• fats• proteins(c) describe and carry out tests for:• starch (iodine in potassium iodide solution)• reducing sugars (Benedict’s solution)• protein (biuret test)• fats (ethanol emulsion)(d) state that large molecules are synthesised from smaller basic units:• glycogen from glucose• polypeptides and proteins from amino acids• lipids such as fats from glycerol and fatty acids

33 Fats & OilsFats are made up of carbon (C), oxygen (O) and hydrogen (H).Fats produce twice amount of energy of carbohydrates.Fats broken down by hydrolysis to a Glycerol head and 3 Fatty acid tails.

34 Test for Fats Emulsion TestAdd 2cm3 of ethanol to the substance in a test tubeShake the test tube.Add 2cm3 of water.+ve resultWhite emulsion

35 Functions of Fat Provide a source & storage of energyProvides insulation to prevent excessive loss of heat.Solvent for fat-soluble substances (vitamins, minerals)Part of the cell membraneReduce water loss from skinPrevent organs from physical injuries.

36 5094 Pure Syllabus (a) state the roles of water in living organisms.(b) list the chemical elements which make up:• carbohydrates• fats• proteins(c) describe and carry out tests for:• starch (iodine in potassium iodide solution)• reducing sugars (Benedict’s solution)• protein (biuret test)• fats (ethanol emulsion)(d) state that large molecules are synthesised from smaller basic units:• glycogen from glucose• polypeptides and proteins from amino acids• lipids such as fats from glycerol and fatty acids